ASQ - Statistics Division

Reliability: The Other Dimension of Quality – 2002 Youden Memorial Address

Abstract: The address explores the relationship between quality engineering, reliability engineering, and statistics. Reliability is “the probability that a unit will survive until a specified point in time under encountered use conditions.” The challenge is to design a product such that it will be robust to the expected environmental “noises” that a product will encounter during its manufacture or operation. Reliability assurance is a procedure based on reliability modeling and that combines information from various sources, including: knowledge of system structure, possible failure modes and their effects on system operation, reliability data for individual components and interfaces, etc. Design for Reliability programs exist for ensuring that a product will have desired levels of reliability by focusing on eliminating problems before they occur. They include Design for Six Sigma (DFSS) with its DMADV steps: Define, Measure, Analyze, Design, and Verify. Failure modes are a key consideration in “Design for Reliability”. Many tools like failure modes and effect analysis (FMEA) and accelerated life testing (HALT) exist to anticipate and eliminate these problems up-front. In many applications, engineers use a predictive model to anticipate a product’s reliability in the field. These models use previous experience, engineering knowledge, analyses based on physical/chemical models that relate to failure, physical experimentation and accelerated testing. Uncertainty may be quantified using Bayesian methods. Concluding comments include: a. warranty data can provide feedback for improving existing products and for designing new ones, b. statisticians should be part of reliability teams, and c. speed-up-the-clock tests do not follow basic principles of experimental design.

Keywords: Reliability demonstration - Reliability assurance - Bayesian - Design for Six Sigma (DFSS) - DMADV (Define - Measure - Analyze - Design - Verify) - Design for reliability - Failure modes and effect analysis (FMEA) - Highly accelerated life testing (HALT)

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